The invention relates to a magnetic reading head which is capable of generating a signal which is a measure of the azimuthal position of the gap of the head relative to the longitudinal axis of an information track to be read on a recording medium.
In playing back information stored in tracks on a recording medium, it is of great importance that during the playback process the correct azimuthal position of the gap of the head relative to the selected track should be maintained. An incorrect azimuthal position of the gap has for its result that the higher frequencies of the information signal are poorly reproduced. For example, a deviation of only a few minutes from the correct azimuthal position may reduce the reproduction of the high frequencies of an audio signal by some KHz. This problem occurs inter alia when the information has been recorded on the recording medium by means of an apparatus other than that with which it is played back at a later time.
An efficacious method with which a correction of the position of the head gap relative to a selected track is made possible is the subject matter of the patent application Ser. No. 041,674, now U.S. Pat. No. 4,317,144, filed simultaneously with the present patent application. This method is based on the fact that the upper half and the lower half of a selected information track are simultaneously scanned individually, the phase difference between the two scanned signals being measured. A control signal with which an electromechanical converter is controlled which corrects the azimuthal position of the head (gap) is derived from the phase difference. Since the determination of the phase difference between the two scanned signals may present difficulties due to the irregularity thereof, the time difference between two associated zero passages of the scanned signals is preferably measured.